1. Field of the Invention
The present invention relates to a vacuum processing method using oxygen radicals for processing an object to be processed in a processing chamber defined by a vacuum vessel, and a vacuum processing apparatus for carrying out the same.
2. Description of the Background
Semiconductor wafers for fabricating ICs and glass substrates for liquid crystal displays, etc. (hereinafter referred to as xe2x80x9cobject to be processedxe2x80x9d or xe2x80x9cobjectxe2x80x9d) are processed by a process, such as an etching process or an ashing process, by a vacuum processing method using a vacuum processing apparatus. The vacuum processing method and the vacuum processing apparatus place an object in a processing chamber defined by a vacuum vessel and process the object in an evacuated atmosphere.
Conventional vacuum processing methods and apparatus for carrying out the same include a chemical dry etching (CDE) method and an apparatus for carrying, out the same which produce radicals in a plasma producing chamber separated from a processing chamber by activating a process gas, and introduce the radicals into the processing chamber to etch a thin film formed on a surface of the object placed in the processing chamber with the radicals.
Conventional vacuum processing methods and apparatus for carrying out the same further include a reactive ion etching (RIE) method and an apparatus for carrying out the same which produce a plasma by applying a radio-frequency voltage to a process gas supplied into a processing chamber, and etch an object placed in the processing chamber with the plasma produced in the processing chamber, and a microwave plasma etching method and an apparatus for carrying out the same which produce a plasma by exciting a process gas supplied into a processing chamber by applying a microwave to the process gas, and etch an object placed in the processing chamber with the plasma.
When an object is processed with oxygen radicals by the conventional vacuum processing method and the apparatus for carrying out the same, organic structural members and organic adhesives are etched if they are exposed to oxygen radicals in the processing chamber.
Referring to FIG. 6, an electrostatic chuck 28 for fixedly holding an object is placed on a support surface 3a of an object support table 3 place in a processing chamber. The electrostatic chuck 28 has an electrode sheet 29, and electrode covering sheets 30 sandwiching the electrode sheet 29 therebetween.
The electrode covering sheets 30 are formed of a heat-resistant polymer, i.e., an organic material, such as a polyimide. The lower electrode covering sheet 30 is bonded to the support surface 3a of the object support table 3 with an organic adhesive 32.
Since the electrode covering sheets 30 and the adhesive 32 are formed of organic materials, portions of the electrode covering sheets 30 and the adhesive 32 exposed to an atmosphere in the processing chamber are etched by oxygen radicals for processing the object.
Since the components formed of organic materials and exposed to the atmosphere in the processing chamber are etched by oxygen radicals, the components of the vacuum processing apparatus, such as the electrostatic chuck, are short-lived and are sources of particles that reduces the yield of products. Essentially, the vacuum processing apparatus using oxygen radicals must avoid using organic materials. However, the use of parts formed of organic materials in such an vacuum processing apparatus is unavoidable in the present circumstances because of requirements for machining parts or for the common use of parts.
Accordingly, it is an object of the present invention to provide a vacuum processing method and an apparatus for carrying out the same capable of preventing the etching of parts formed of organic materials and exposed to an atmosphere in a processing chamber even when an object is processed with oxygen radicals.
According to the present invention, a vacuum processing method of processing an object to be processed with an oxygen radical in a processing chamber defined by a vacuum vessel of a vacuum processing apparatus comprises the steps of: fluorinating a surface of a component formed of an organic material and exposed to an atmosphere in the processing chamber with a fluorine radical produced by activating a fluorinating gas containing at least a fluorine atom with the vacuum processing apparatus before carrying the object into the processing chamber; carrying the object into the processing chamber; and processing the object with the oxygen radical produced by activating a process gas containing at least an oxygen atom.
The term xe2x80x98radicalxe2x80x99 as used in the description denotes a chemically highly active atom or molecule. Sometimes, radicals are referred to as xe2x80x98active speciesxe2x80x99.
Preferably, the vacuum processing apparatus comprises an object support table disposed in the processing chamber to support the object thereon, and an electrostatic chuck mounted on a surface of the object support table to hold the object on the object support table, and the electrostatic chuck comprises an electrode, and an electrode covering sheet covering the electrode. The organic material is that forming the electrode covering sheet and an organic adhesive bonding the electrostatic chuck to the surface of the object support table.
Preferably, the vacuum processing apparatus comprises an object support table disposed in the processing chamber to support the object thereon, an electrostatic chuck mounted on a surface of the object support table to hold the object on the object support table, and a protective sheet of a fluororesin covering the electrostatic chuck to protect the same. The organic material includes an organic adhesive used to bond the protective sheet.
Preferably, the fluorinating gas is a mixed gas including a gas containing at least a fluorine atom and an O2 gas.
Preferably, the gas containing at least a fluorine atom is one of CF4, C2F6, C3F8, NF3 and SF6, or a mixture of some of these gases.
Preferably, a ratio of a flow rate of the O2 gas to a flow rate of the fluorinating gas including the O2 gas is 40% or below.
Preferably, the process gas contains at least an O2 gas.
Preferably, the process gas and the fluorinating gas are activated in a plasma producing chamber separated from the processing chamber, and the fluorine radical or the oxygen radical is supplied into the processing chamber.
Preferably, the object processing step processes the plurality of objects successively, and the fluorinating step is performed after the object processing step, and the object processing step and the fluorinating step are repeated alternately.
The vacuum processing method according to the present invention fluorinates the component formed of organic material and exposed to the atmosphere in the processing chamber with the fluorine radical, and then processes the object with the oxygen radical. Fluorinated surface layer of the organic component serves as protective film to prevent the etching of the component formed of the organic material with an oxygen radical.
A vacuum processing apparatus according to the present invention comprises: a vacuum vessel defining a processing chamber to be evacuated; radical producing means for producing a fluorine radical by activating a fluorinating gas including at least a fluorine atom and for producing an oxygen radical by activating a process gas containing at least an oxygen atom; gas supply means for supplying the fluorinating gas or the process gas to the radical producing means; and an object support table disposed in the processing chamber to support an object to be processed thereon; wherein a surface of a component formed of an organic material and exposed to an atmosphere in the processing chamber is fluorinated by the fluorine radical, and then the object is mounted on the object support table and processed with the oxygen radical.
A vacuum processing apparatus according to the present invention comprises: a vacuum vessel defining a processing chamber to be evacuated; radical producing means for producing an oxygen radical by activating a process gas containing at least an oxygen atom; a gas supply means for supplying the process gas to the radical producing means; an object support table disposed in the processing chamber to support an object to be processed thereon; an electrostatic chuck mounted on a surface of the object support table to hold the object on the object support table; and a protective sheet formed of a fluororesin and covering the electrostatic chuck to protect the electrostatic chuck.
Preferably, a surface of a component formed of an organic material and exposed to an atmosphere in the processing chamber is fluorinated with a fluorine radical produced by activating a fluorinating gas containing at least a fluorine atom with the radical producing means.
Preferably, the fluorinating gas is a mixed gas including a gas containing at least a fluorine atom and an O2 gas.
Preferably, the gas containing at least a fluorine atom is one of CF4, C2F6, C3F8, NF3 and SF6, or a mixture of some of these gases.
Preferably, a ratio of a flow rate of the O2 gas to a flow rate of the fluorinating gas including the O2 gas is 40% or below.
Preferably, the process gas contains at least an O2 gas.
Preferably, the radical producing means has a plasma producing chamber separated from the processing chamber, and the radical produced in the plasma producing chamber is supplied into the processing chamber.
Preferably, a cycle of fluorinating a component formed of an organic material and exposed to an atmosphere in the processing chamber and successively processing a plurality of objects is repeated.
The vacuum processing apparatus according to the present invention fluorinates the surface of the component formed of the organic material and exposed to the atmosphere in the processing chamber with the fluorine radical, and then processes the object with the oxygen radical. The fluorinated surface layer of the component serves as protective film to prevent the etching of the component formed of the organic material with the oxygen radical.
The vacuum processing apparatus according to the present invention is provided with the protective sheet of a fluororesin covering the electrostatic chuck. Therefore, the etching of the electrostatic chuck with the oxygen radical can be prevented by the protective sheet covering the electrostatic chuck.